Scale effect of vegetation index based thermal sharpening: A simulation study based on aster data

Vegetation index based thermal sharpening technologies have been studied recently. Previous studies showed that the relationship between vegetation index and surface temperature is independent with spatial resolution; consequently, the relationship established on coarse resolution can be applied on fine resolution. However, in this study, we found that the resolution independence can not grant the effectiveness of the sharpening method. Instead, relationship of vegetation index temperature established on the correct spatial size (size of thermal resolution) should be used for sharpening temperature image. Unfortunately, the relationship of vegetation index temperature on different spatial sizes varies greatly. Therefore, previous methods which apply the relationship established on the whole image to the small spatial size (size of thermal resolution) may produce large error. In this paper, an improved vegetation index based sharpening method considering the effect of spatial size was proposed and tested by a simulation study. The result shows that it can acquire higher sharpening accuracy than original method.